Method and apparatus for tone control of sound reproducing systems



March 18, 1941. J. M. BAXTER 2,235,249

METHOD AND APPARATUS FOR TONE CONTROL OFZSOUND nsrnonucme sYsTEMs' FiledJan. 28,. 1959 kutatm 1 INVENTOR.

, H 7055p, MEHXTEK BY 2.. w

' Patented Mar. 1 4 v i f: I 1 3 I i "ascetic;

menu It ran warns, Idtfiuiinibfto v i so as I a tone control in whichthe middle register may inrelation:

" I spectivelyvby B, M and-T, are provided; These by way of example --toa combined phonograph j and radio. The phonograph portion includes a iiiThis invention relates to a method and appsratusfor tone control orelectric sound rem ducing. systems such .as are found in radio"receivers, phonographs and-sound film apparatus. 5 v In tone controlapparatus heretofore commonly employed for diiierentiating theampliilcation ci the upper and lower registers of sound, itha's been theusualpractice when it is desired to accentuate the bass register firstpartially sup.- press the treble register 'andthen increase the entirevolume level 'oi'the output. Thus twooperations are-necessary each timethe accentu ation of 'the bass register i adiusted, and the canal resultof the adjustment cannot be determined until the second operation iscompleted. The two operations often must be repeated several timesbeforea stitlsiactory adjustment is obtained.--' Other tone controladjustments require similar manipulation. 4

One object o! the present invention is to pro-- vide a tone'control bymeans of which either the upper. or lower register may beaccentuated orsuppressed without the necessity of 1 altering the general volume levelat the same ti'me.- 1 1 "Another object or the invention is to providealso be T accentuated or suppressed the bass and t'enor'registers. i V

Other objects and features of'theinvention will be understood fromtheaccompenying draw-' ingand the following description and claims: The-drawingis a diagram of electrical conneov I. tions by means of whichthe inventionmay be practiced; I

" In the drawing the invention isshown applied pickup it which may be ofthe; common mag netic type and isconnectedtoa load circuit oohi sistingof conductors ii and ,ilwith a, load resistance i3- connectedtherebetween. The con-. ductor. ii is connected to a movable linger llof a program switch II and the conductor II is grounded at GM. In theposition of the program circuits the load circuit oi the pickup andrenders is turned tothe' position for phonograpnoperation, the ringer Itconnects the conductor II to a conductor it which i connected through apotcn+ jtiometer I! to ground atqll; j g

The radio portion of the apparatus includes .an input circuit consistingof. antenna," and 55 grounded conductor II which are connected to 70mm."'iot'nLiif";

'tentiometer 2I grounded at G21: This ilnger is also iconnectedby'aconductor 28 to fia potenconnected toa e potentiometerlflnger Ill. The

trols the input to all threeof the tubes ;B,-'M.and

. .input tothe tube B only, and that of .therfingerr switch 15 showninthe drawing, the finger l4 engages a branch of conductor II and thusshort J aipreampllner and detector unit 28 supplie'dwith,

power irom any suitable-"source by conductors.

2i. unit may befof any suitable type I 'ad'a'pted'j to" receive theenergy from the input circuit and toamplity and change-the characteristics ther'eoi' to approximately those {or energy received inthe'phonograph; circuit. The-output oi the un'it 2| is 'deliveredito acircuit including aconductorxll grounded at-G22 anda' conductor; 28connected to'a finger 24 of the program switch '1 ".1 In the-position ofthe switch shown in the drawing, the linger 24 connects the conductor 28to the conductor It and thus delivers the'out- .put oi the radioapparatus to thepotentiometer 11. When the program switch isItu'rned tothe phonograph-position this connection is broken and-the radio portionof the a m n perative.--' g I .kmovabie'flngcr 2i engages thepotentiometer t II and is connected by a conductor "to a D0- tiometer isgrounded at-02s.: The potentiometer '21 is provided with a contact,finger, and the 'potentiometer 1O -is:;providedwith a similar finger-IL?i Three: electron discharge tubes, indicated re tubee'may be of anysuitable type for amplificagrids 34-. The cathodes are grounded throughthe usualrbiasing resistorsshunted by condensers St'tThe; controlgrid-o1 the tube his control grid of the tube M 'isiconnectedto thepotentiometer finger :2! and that of the tube T is connected to thepotentiometer finger ll. It

will "i be apparent irom the foregoing that the p adjustment. of thepotentiometerv flnger,=-:2I con- ,I. The adjustment-"oi! the fl'nge'rlll controls the Ii controls the input to the tube .T only.

Power for maintaining the proper j ode voltages is obtained byimpressingonga pair or conductors 8] a unidirectional voltage from anysuitable source. One. of iaid conductors is grounded at G" and thefotherls' connected to 1 the several anodes}! through. resistors II, 39, .0,and connected as shown in the drawi'ng and prop'tnj7tioned toprovide-each of-gthe anodes with h Proper o era in l btent nltw 1 Mind.r?

The anode circuits of the tubes :3,

are all coupledto an amplifier, but each 0! register;

connections is provided'with suitable filteringmeanstolimittheoutputoithetuhestothebm,

' 'middlc-and treble oi the band of audio irequenciearespectively; Thus.the snodeotthe a tube Bis connectedto the ampliiier ll throushacondenser 44, a'resistoril l and a resistor 6L A condenser 41 shunts thecircuit to mm at 041mm a point between theresistors and as. In the'.-i'drawing"thejohmic;valuel or th "resistors and the a the is apredetermined arbltrarypoint selected to define the upper limit ofthebass muster." sim larly. the tube '1' hasits anode coupled to theamplifier 48 through a condenser II. This condenser is resistor .4i',, acondenser ll and.a resistor N; A

; I condenser ii shunts the anode to ground at G"; 4 1 These resistorsand condenserswhen proportioned v as indicated; inthe,drawing,constitute.a broad v .30 band-pass filter which suppressesparts of the upper and lower registers 01- the outputs! vthe tube M andpasses aband ot irequencies overlap in .,th5 tpassed byithe ba'ss'andtreblecircui-ts; y f The amplitler has its second inputterminai ggrounded atG and may beisupplied with operating power e by conductors 752 connected to sultablesourceof power. Q- A' loud speaker I! isconnectedto the amplliier'in-theiusual manner I by a cableconnection54.; 'Theamplifler ,4! may be o! well-known torm adapted-to receiveQhGQQlItI-IFOI the tuhesB, M and T-andto amn plif'ythe same :tospeakerlfevel. -11 dmsepa- -;.'rate.amp1iner's may be usedioreachbtthess. .nusecircuitslbe a From the formal P 9- n l m m m Y orenergytransmi-ttins circuits to V parent that the bass register maybeaccentuated i may be accentuated .or' suppressed by adjustment 'rhethodotherwis'edrequired.

:11 it-is'desired to accentuate the middl e'r siltor, both the bassandtreble maybe suppressed Y and the general volume level raised.-

thisre 5, spect the method of adiustmentis similar in the prior practicein requiringmore than one opera {cuitaswell. j a a V g The-foregoingspecification des'crlbesithe in l vention in oneof its preferred-forms,'th e details 5 *of' which may-me varied without departing from thescope or the invention as 'deflnedby the ap- ("pended claims; Itisthought-that the applicamesses translatingethecutputth'ereot intosound.

,theinputsto allo! said channelsein or decreased by adiustmentrot the ll-togincrease oredecrease the input to the tube 3 without therebychanging the "general volume' level-of the output. Slmllarlmthetrebleregister in each circuittadapted .to s ption 9! beobvious.

Theinventionclaimedis: 7

i. A method ottone control for anelectronic; soundreproducins systemconsisting in dividing! the energy input to thesystem into bass,andtreblechannelacontrcllingtheamplitudeoiinput toall-oi' common, in,dependently amplitude of the in-' put to the bass and trehlejchanhels,altering ther o energy in the several channels to suppressi'requenciesabovethebassregisterinthebcsschan nel, to frequencies belowthe treble TU- ister-in the-treble channel and to suppress. at least apart 01 the bass and treble frequencies in is the middle and thenuniting the output orfalroi said channels in a single channel andtranslating the output thereoi into sound. p of relatively lowcapacitance'asindicat'ed inthe 2o example of the drawing and thussubstantially, connnesthe output of the tube '1 to the treble 4 Bysuitably proportioning convdenser, the lower limitoithe treble registerp belarbitrarily chosen as'desired." The output 0! r c 5 the tube M isfed to the amplifier .40 throughthe 2.1. A'method of tone control for anelectronic i sound reprodudngmystem consisting 1o! dividing go the enUinput-tothesysteminto aplu'ralityoi separate channels. iiltering theeuergyin each oi said channeisto suppress certain portions of the Jaudio-irequency band in each channel, independentlyicontrollinguthe'ampiitude oi the output 0115, some oisaid channels.andunlting the output-oi allot said; channelsiinfla single channel and eV 3. A method 01- tonelcontrolior an electronlclzi. 1- soundgrcproducihgsystemconsisting in dividing theenersy input to the systeminto bass.middle and treble channels, controiling'the amplitude 011-;

common,in.- dependently controlling the amplitude of theinput to thebass and treble channels, filtering the ,1

energy inthe several channelsto suppress 'ir'e I quencies sbov'ethebas'sbass chan-i nel, to suppress irequenciesbelowthe treble reslater intreblechannei-and to suppress at least a part oithe bass and'trebiefrequencies in 4. Apparatusiorl 'lcontrolbss'anelectronic receive apartor theinput energy of said system; 7

press certain portions oithe audio-frequency band, a separateloiumecontrol unit associated with ot said circuit a' .iurther volumecontrolunit connectedftocontrplthe generaivol ume level of all 'oi'isaldcircuits, and means re-"-.v ceiving-the, combined output'ener'sy of" allof said I i circuits and converting the same into sound." 5. Apparatusfor. tone-control oi an-electronic I sound reproducing system includings; plurality ot-energy transmitting circuits each connected to, a

receives part0! the input energy of said'system,

filtering means in each circuit adapted to suppress ,cert'ain portionsoi' the audio lrequency 1 mume cchtrer nit m iseeu Y with Q. ul' l, afurther .yolume as V control unit 'con'nected'to control theseneralvoltion." However, it is obvious that a fourth potentiometer inserted inthe middle register circuit will provide independent adjustment or thatcirume level of all'otsaid circuits, a separate, amplitying meansin'e'ach oi said circuits, and'jmeans' receiving the combined output[energy of allflot' 'f 'i l d c nve ins t e M 1m sound. 7

6. Apparatusior tone control of an electronic sound reproducingsy'stemincluding a plurality of energy transmitting circuits ea h connected to,4, receive a part or the input energy of said system.

a in one of said circuits, adapted to confine the output thereofsubstantially to the bass register of'the audio-frequency band, a filterin another of saidcircuits adapted to confine the output'thereofsubstantially to theltreble register,

filters in a. third of said circuits adapted to suppress at least a partof the bass and treble registers therein, separate volume control unitsin the bass and treble circuits, a thirdvolume control unit connected tocontrol the volume level in all of said circuits; and means receivingthe com-- bined output energy of'ail of said circuits and a filter inone ot said circuits adapted to confine the output thereof substantiallyto the bass' regis ter of the audio frequency band, a filter in' anotherof said circuits adapted to confine the output thereof substantially tothe treble register,

press at leasta part of the bass and treble register therein, separatevolume'control units in the bass and treble circuits, a third Volumecontrol unit connected to control the volume levelin all 10 ofsaidcircuits, a. separate amplifying means in each of'said circuits, andmeans receiving the combined output energy of all of said circuits andconverting the same into sound.

JOSEPH BAXTER.

filters in a. third of saidcir'cuits adapted tosup-

